In electronic packet networks, packets are usually launched into the network without negotiation and, when competing streams of traffic meet at a congesting node, elastic buffering is used to handle the collision caused by the coincident arrivals of traffic for the same destination. Transmission protocols, such as the Transmission Control Protocol (TCP), are used to ensure that the average rate of traffic arriving at a switching node is not greater than the outgoing link capacity. Buffer fill in the switching nodes is usually used as the trigger for indicating congestion to those protocols.
In purely optical networks, elastic buffering of information is difficult, if not impossible, to implement and manage. Thus, once a unit of data is launched into the network, it must either follow its switched path through the network without hindrance or, if it collides with traffic from another source at some switching point, one or both units of data must be discarded. The same situation occurs in any other type of network in which buffering of coincident arrivals of traffic for the same destination, or of transient overloads, is not practical or desirable, for example multi-hop satellite networks.
Existing solutions to this dilemma include the application within the bufferless networks of statistical techniques that accept collision and loss but minimize collisions by randomizing the timing of traffic bursts. Unfortunately, such techniques are inefficient in bandwidth use.
Another solution is the implementation of a completely synchronized network such that all collisions are avoided. In a completely synchronized network, a sender can be allocated specific time intervals at which to send data. A signaling mechanism and/or centralized controller is needed to manage the allocation of timeslots, and clocking and framing have to be provided on a network wide basis. Unfortunately, the cost of such a solution is the complex requirement for network wide synchronization and a necessity to make slow changes of bandwidth allocation based on total knowledge of demand and resource.
The background information herein clearly shows that there exists a need in the industry to provide an improved method and apparatus for performing collision avoidance in a bufferless network.